Ferric Chloride

Ferric Chloride or Iron (III) Chloride (FeCl3) is used as a flocculant in sewage treatment and drinking water production. When small quantities of ferric chloride are added to the raw water, iron(III) hydroxide precipitates and adsorbs finely divided solids and colloids.
It is usually produced and marketed as a concentrated solution with a minimum concentration of 40% w/w. Starting from this solution is also possible to produce a solid crystallized Ferric Chloride with 37°C melting point.

Consito developed know-how and technologies for ferric chloride 40% w/w solution production plants, both for waste water treatment and drinking water grades.
We can provide for some different processes to produce ferric chloride, according to the feedstock:

Iron scraps and chlorine gas, by ferric chloride recycling

Soft iron and chlorine gas, by ferric chloride recycling

Ferric oxide and hydrochloric acid

Mixed oxides, hydrochloric acid and chlorine gas

Pickling liquors and chlorine gas, with final concentration

The raw materials are likewise cheap and easily available so that the manufacture of ferric chloride is frequently an attractive supplement for chlor-alkali producers.

Production process

Ferric chloride 40% w/w solution can be produced by different processes, according to the feedstock.

Iron scraps

Ferrous chloride is obtained by contact of ferric chloride with iron into a dissolution vessel, according to the following reaction:

Fe + 2 FeCl3 = 3 FeCl2

The ferrous chloride solution resulting from iron dissolution is then filtered and oxidized to ferric chloride in the chlorination section by chlorine gas, according to the following reaction:

3 FeCl2 + 1.5 Cl2 = 3 FeCl3

Two third of the ferric chloride solution are recycled back to the dissolution vessel and one third is discharged as product.

Soft iron

This feedstock is a powder of soft iron obtained from rolling-mill process. Production process is analogue to the above description with iron scraps as raw material.

Ferric oxide

Starting from ferric oxide, by product of steel mills, or from hematite, it is possible to obtain ferric chloride by simple reaction with 32% HCl:

Fe2O3 + 6 HCl = 2 FeCl3 + 3 H2O

Mixed oxides

This feedstock is a mixture of ferric oxide and ferrous oxide obtained as scales from rolling-mill process. A previous treatment with 32% HCl followed by chlorination gives place to complete conversion to ferric chloride, according to the following reactions:

Pickling liquors

By a particular process it is possible also to use as feedstock the sludge from steel pickling with HCl. Reduction of chorine consumption is also obtained. Final concentration by evaporation is generally required to reach a 40% w/w solution.

Ferric chloride applications

Ferric Chloride or Iron (III) Chloride (FeCl3) is used as a flocculant in sewage treatment and drinking water production. When small quantities of ferric chloride are added to the raw water, iron(III) hydroxide precipitates and adsorbs finely divided solids and colloids.

In Europe, chemical using of ferric chloride for drinking water is well defined by the UNI EN 888:2005 Regulation.
Applies to iron (III) chloride (a), iron (III) chloride hexahydrate (b) and iron (III) chloride solution (c) for treating water intended for human consumption. It covers characteristics and defines requirements and corresponding test procedures for iron (III) chlorides (a), (b), and (c), together with information on its use in water treatment.

Impurity and main by-products: limit as mass fraction of Fe(III) content in %
Reference: Table 3 - Impurities
Fe (II) has a lower coagulant efficiency compared to Fe(III). Also hydrolysis of Fe(II) starts at pH8 and therefore Fe(II) can remain into the water at lower pH values.
An excess of insoluble matters indicates the presence of foreign matter Iron is a component of the product will usually be removed in the treatment process.

Chemical parameters: limit as mg / kg of Fe(III)

Reference: Table 4 - Chemical parameters
Cyanide (Cn-), pesticides and polycyclic aromatic hydrocarbons are not relevant since the raw materials used in the manufacturing process are free of them. For max impact of iron (III) chloride on trace metal content.